Two developments last week lend credence to the idea that the national political parties are trading places in their approach to the defense industry. On April 3, the Bush Administration's Navy Secretary assailed shipbuilders, complaining of unreliable cost estimates, lack of competition and low investment in new technology. The next day, Senator John McCain (R-AZ) sent a letter to the Air Force Secretary implying the Boeing Company was improperly awarded a contract for helicopters.

What makes these events unusual is that until recently the Navy Secretary was employed by the Navy's biggest shipbuilder, while Boeing Helicopters is one of the largest employers in Senator McCain's state. If you subscribe to the conspiracy theory that weapons purchases are driven by collusion among contractors, legislators and revolving-door executives at the Pentagon, it's hard to explain how either development happened.

What's really happening is that the intelligentsia of the Republican Party is turning away from the defense industry, even as Democrats rediscover the large pool of party faithful employed in defense plants.

The shift isn't hard to understand, because conservative ideology makes Republicans suspicious of any enterprise dependent on the government, while Democrats are naturally attracted to the unionized workforce of the defense sector, one of the last bastions of organized labor in the industrial economy. If you look at the regions where Democrats enjoy greatest electoral strength -- the Northeast, the West Coast, the industrial Midwest -- those are also places where the defense industry is strong. The same is true in swing states where Democrats are gaining ground, such as Colorado, Florida and Virginia.

Still, the shift may seem improbable against the backdrop of post-Vietnam political culture. A generation of Democrats was alienated from the defense establishment by the war, and it became popular among left-wingers to talk of an "iron triangle" setting misguided military priorities.

Republicans, on the other hand, came to see national defense as a core electoral franchise, a convenient way voters could distinguish their party from the anti-war Left. These divergent images led observers to assume that Republican administrations would throw money at defense contractors, while Democrats would be more inclined to look out for enlisted personnel. What observers missed was that soldiers were increasingly voting Republican, while private-sector defense workers were voting Democratic.

Now, the way the two parties view the defense industry may be moving into closer alignment with their electoral interests. Sometimes this trend manifests itself subtly, as when Senator Hillary Clinton (D-NY) declined to echo criticism of the sector expressed by McCain protege Lindsay Graham (R-SC) in a meeting of the Manufacturing Caucus last year.

Other times the trend is more obvious, as in Defense Secretary Donald Rumsfeld's refusal to meet even once with industry executives during his entire tenure. Last week's diatribe against shipbuilders by the Navy Secretary was similar to complaints about the whole sector leveled in 2005 by Rumsfeld's hand-picked acquisition czar, Kenneth Krieg.

Pentagon insiders say that Rumsfeld's successor, Robert Gates, has a similarly jaundiced view of the industry, which would make Gates the third consecutive Republican defense secretary to distance himself from the sector.

Recent Democratic defense secretaries look like industry cheerleaders compared with the draconian cuts that Dick Cheney imposed on the sector when he held that post at the end of the cold war.

So while Republican legislators such as Trent Lott (R-MS) still work hard to help home-state contractors, the ambivalence of Republican Party elites is making it easier for Democrats to rethink their relationship to the defense industry.